In the wet tests for detection of various cations by precipitatio… — Solution | JEE Chemistry

MCQEasyJEE 2023Salt Analysis (Cations & Anions)

In the wet tests for detection of various cations by precipitation, $Ba^{2+}$ cations are detected by obtaining precipitate of :

Answer

Correct answer:B

Standard Method

Given: The cation to be detected is $Ba^{2+}$ in wet qualitative analysis by precipitation.

Find: Which precipitate is obtained for detection of $Ba^{2+}$ .

In wet testing, $(NH_4)_2CO_3$ is used as a group reagent for detecting fifth group cations such as $Ba^{2+}$ , $Ca^{2+}$ , and $Sr^{2+}$ .

The presence of $Ba^{2+}$ is confirmed by formation of barium carbonate precipitate.

The reaction is

Ba^{2+} + (NH_4)_2CO_3 \rightarrow BaCO_3 \downarrow + NH_4^+

Barium carbonate forms a white precipitate when $Ba^{2+}$ reacts with $(NH_4)_2CO_3$ in water.

Therefore, the precipitate obtained is $\text{BaCO}_3$ , so the correct option is B.

Confusing the confirmatory precipitate with $\text{BaSO}_4$ . That salt is also insoluble, but the given wet test here specifically uses $(NH_4)_2CO_3$ as the group reagent. Use the reagent mentioned in the test to identify the correct precipitate.
Choosing $\text{Ba(OAc)}_2$ because it contains barium. This is incorrect because the question asks for the precipitate formed during detection, not any soluble barium salt. Focus on the product formed in the qualitative analysis reaction.
Ignoring group analysis chemistry and selecting barium oxalate by memorizing insoluble salts. In wet qualitative analysis, the prescribed group reagent determines the precipitate. Here, carbonate precipitation is the relevant test.

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